The prior art speed wrench as shown in FIG. 1 comprises a handle 1a and movable jaws 1b and 1c which are placed at two ends of handle 1a. The inner edge face of movable jaw 1b forms an unsealed polygonal mouth which can match the fixed jaw 1a' formed by ends of handle 1a so as to clamp various differently sized work pieces such as a screw nut or a screw bolt and execute the locking or releasing work on the work piece. At the central part of the movable jaw 1c, there is a hollow polygonal hole. The polygonal hole can match fixed jaw 1a' formed by one end of handle 1a to permit the tightening or releasing of the speed wrench on the work piece as above mentioned. This kind of speed wrench is more convenient to operate than the usual adjustable wrench. When one uses a conventional speed wrench and applies force to a work piece, the hand of the operator must be used to help adjust the movable jaws 1b and 1c to fix and clamp the work piece. Thus, the aforedescribed speed wrench is impractical.
An improved speed wrench as shown in FIG. 2 has a spring sheet 2d in the axial slot of handle 2a. One end of said spring sheet 2d is fixed at one side of handle 2a while another end pushes against the lower end of movable jaw 2b. Due to the tension of said spring sheet (d), the movable jaw 2b and the fixed jaw 2a' formed by the end of handle 2a are matched together to clamp the work piece tightly. This improved speed wrench does not need a helping hand to adjust the movable jaw 2b while applying force to the work piece.
However, the design of the speed wrench of FIG. 2 suffers from other disadvantages. At the time movable jaw 2b is pressed by the tension from spring sheet 2d to the fixed jaw 2a' to close the members together, the user must thereafter use his hand to open the movable jaw 2b to adjust the movable jaw 2b so as to permit the speed wrench to be applied to the work piece. Accordingly, the speed wrench of FIG. 2 is also impractical.
The above described conventional speed wrench devices have essentially the same defects. That is, if a working piece is placed between a gap or when available space is very narrow, it is difficult to fit the speed wrench to the work piece and thereafter apply the desired force or even to adjust the speed wrench to fit the work piece. Thus, the practicality of either of the above-described conventional speed wrenches is limited.